1. Field of the Invention
The present invention relates to a process for the production of activated carbon or coke from a moist organic substance, and it relates in particular to a process in which a moist organic substance is first mixed with hot flue gases in a drying zone, whereafter the dried organic substance and an oxygen-bearing gas are directed into the coking zone for a controlled burning of the volatile constituents of the organic substance, then the coked final product is separated from the gas or, alternatively, the product emerging from the coking zone is directed into the activation zone, where it is mixed with hot, moist gases, and finally the gases are separated from the activated carbon. The invention also relates to a cylinder furnace assembly for carrying out the above process.
2. In connection with the mechanical processing of wood, a great deal of moist residues are produced. Attempts have been made to exploit these residues by burning them. However, the high moisture content in the residue lowers the amount of thermal energy obtained from it. Milled peat used for fuel, even air dried, contains a large amount of water. Also, in furfural production a furfural residue is produced which is rather finely divided and moist (moisture content approx. 40-50% by weight). This residue contains only some ash and a large amount of carbon and volatiles. It can also be destroyed by burning.
The benefit derived from the burning of the above organic, finely-divided substances, which contain large amounts of water, carbon and combustible volatiles, is decreased by their high moisture content. Furthermore, the burning of such substances by means of conventional combustion apparatuses is inconvenient.
In attempts at using the above organic substances in, for example, the production of activated carbon, they are in general at least partly dried, whereafter they are usually first charred and then activated using water vapor. The investment and operating costs of such previously known production processes for activated carbon are, however, considerably high, owing to the several separate treatment stages and the high energy requirement, especially when using superheated water vapor for the activation. When block peat is used as the raw material for activated carbon and when the water vapor activation is carried out in a cylinder furnace, a long reaction period is necessary and the mechanical strength of the product is low. The activated carbon thus produced is not suitable where a high mechanical strength is required of the carbon.
German Patent Application No. 2,606,368 discloses an apparatus in which the coking and the activation are performed in the same rotating furnace; however, in this furnace the coking zone and the activation zone have been separated by means of a partition. In this apparatus the coked substance is cooled with water and the produced water vapor is directed into the activation zone. This apparatus is not as such applicable to a moist residue but only to a dried residue.